The present invention relates to a door closer in general, and more particularly to a door closer of the type capable of holding the door in a partially or fully open position.
There are already known various automatic door closing arrangements which are usually spring-biased to urge the door towards its closed position, and which almost invariably include damping arrangements of different types which prevent the door on which any of such closing arrangements is used from closing too rapidly and/or too noisily.
In one of the conventional door-closing arrangements of the above type, which is known, for instance, from the German published patent application DOS No. 2,303,934, there is provided a cylinder-and-piston unit the movable member of which is acted upon by a spring urging the same toward a rest position which corresponds to the closing position of the door. In this arrangement, the two compartments in which the piston subdivides the interior of the cylinder communicate with one another via a plurality of passages in which there are located various valves, such as a throttle valve, an electromagnetically operated valve, and at least one pressure-relief valve or a one-way valve. One of the compartments, which will be hereafter called a pressure compartment in that a damping medium in this compartment is at an elevated pressure as long as no external force is exerted upon the door, communicates with the other compartment, which will be hereafter referred to as a supply compartment in that it holds a supply of the damping liquid, via three channels or passages in one of which there is arranged a constriction and, in series therewith a holding valve which is held in its closing position by an electromagnetic arrangement provided that the latter is energized. Another of the above-mentioned passages or channels incorporates a one-way valve which opens in direction into the pressure compartment, the remaining channel or passage including a pressure relief valve which opens when the pressure within the pressure compartment substantially exceeds the normal operating pressure prevailing in such pressure compartment, that is, the pressure which is attributable to the action of the spring on the displaceable member of the cylinder-and-piston unit. Such pressure resulting in opening of the pressure-release valve may come into existence, for instance, when an external force acts on the fully or partly open door in the direction toward the closed position of the door, in addition to the force exerted upon the displaceable member of the cylinder-and-piston unit and, via the same, also on the door. In other words, the pressure-relief valve renders possible the overriding of the action of all the other valves and manual closing of the door regardless of the fact that the door may be originally held in a partly or fully open position by the electromagnetically operated valve.
As already mentioned above, the door closer of this type is capable of holding the door in connection with which the door closer is used in any desired partly or fully open position, owing to the presence of the electromagnetically operated valve, the electromagnet of which may be energized at will to close the passage associated with the electromagnetically operated valve to thereby arrest the displaceable member of the cylinder-and-piston unit in the then assumed position, thus preventing the door from moving toward the closed position. Of course, the door can still be manually opened to a greater extent due to the action of the one-way valve which permits flow of the damping fluid from the supply compartment into the pressure compartment, and can be manually closed by exerting a force on the door which is sufficient to open the pressure-relief valve to thus let the damping fluid escape from the pressure compartment into the supply compartment. On the other hand, when the electromagnet of the electromagnetically operated valve is de-energized, the pressure of the damping fluid in the pressure compartment will open the electromagnetically operated valve and the fluid will flow from the pressure compartment into the supply compartment, thus permitting the spring to displace the displaceable member of the cylinder-and-piston unit toward the rest position thereof with attendant closing of the door. The speed at which the door will move towards its closed position is determined by the size of the constriction of the throttle valve arranged in series with the electromagnetically operated valve.
This door closing arrangement is advantageous in many respects in that it permits manual adjustment of the position of the door whether or not the electromagnetically operated valve is in its open position, and also permits automatic closing of the door upon simple de-energization of the electromagnet which operates the electromagnetically operated valve. However, experience has shown that, up to a certain degree of partial opening of the door, it is disadvantageous if the door is held in such a partially open position by the electromagnetically operated valve, in that the door must be closed from such a partially open position either manually, or by deenergizing the electromagnet of the electromagnetically operated valve. Under many circumstances, however, closing of the door from such partly open position is highly desirable.